A known variable valve timing control apparatus which restrains deviation, or fluctuation of a relative rotational phase when a vane portion of a driven side rotation member is in contact with a partition portion of a driving side rotation member is disclosed in JP2011-256772A (i.e., hereinafter referred to as Patent reference 1). According to the known variable valve timing control apparatus, the driven side rotation member (vane rotor) is housed in the driving side rotation member (housing), the driven side rotation member and the driving side rotation member are sandwiched by a cover and a sprocket which are formed in plates shape, and the driven side rotation member, the driving side rotation member, the cover, and the sprocket are fastened by bolts.
According to the construction disclosed in Patent reference 1, plural partition portions are formed on the driving side rotation member to inwardly protrude, and plural vane portions (vanes) formed on the driven side rotation member are fitted into the driving side rotation member between the plural partition portions. Thus, retarded angle chambers and advanced angle chambers are formed between partition portions and vane portions. By supplying an operation fluid to one of the retarded angle chamber and the advanced angle chamber, selectively, the driven side rotation member is relatively rotated.
According to the construction disclosed in Patent reference 1, a protruding portion which protrudes in a retarded angle direction is formed on one of the plural valve portions, and a protruding portion which protrudes in an advanced angle direction is formed on another one of the vane portions. According to the variable valve timing control apparatus disclosed in Patent reference 1, a limit of a relative rotational phase is defined by the contact of one of the protruding portions with a bolt when the relative rotational phase reaches a most retarded angle and by the contact of the other one of the protruding portions with a bolt when the relative rotational phase reaches a most advanced angle. According to the foregoing construction, a deviation or fluctuation of positional relationship between the driving side rotation member and the sprocket is restrained while avoiding a direct contact between the vane portion and the partition portion, thereby solving a drawback that the most retarded angle and the most advanced angle fluctuate from predetermined phases, respectively.
According to the construction which restrains a direct contact between the vane portion and the partition portion as disclosed in Patent reference 1, structures of the driving side rotation member and the driven side rotation member are complexified because a recessed portion which receives the protruding portion is formed on the partition portion. Further, with the construction in which the protruding portion comes in contact with the bolt, a contact portion of the bolt with which the protruding portion comes in contact may be deformed or may be worn away in a case the protruding portion repeatedly comes in contact with the bolt because the bolt is formed in a rod shape and a contact dimension relative to the protruding portion is relatively small, which may bring a drawback that a relative rotational phase of the most retarded angle or the most advanced angle is fluctuated from the predetermined phase.
The construction that the vane portion of the driven side rotation member comes in contact with the partition portion of the driving side rotation member for determining the position of the most retarded angle or the most advanced angle according to the known variable valve timing control apparatus is formed in a simple configuration and can be readily manufactured. However, the driving side rotation member and the driven side rotation member may move, or shift about a rotation center in a state where an operation fluid is not adequately supplied, for example, at a start of an internal combustion engine so that the partition portion and the vane portion contact hard repeatedly. In the case where the partition portion and the vane portion contact hard, the partition portion may be plastically deformed, for example, being buckled, alternatively, the partition portion may be immobilized while being elastically deformed by a fastening force which acts on the partition portion in an axial direction by a fastening member, which may deviate, or fluctuate a relative rotational phase of the most retarded angle or the most advanced angle from the predetermined relative rotational phase.
Thus, in a case where the relative rotational phase of the most retarded angle or the most advanced angle, which is determined by a contact of the vane portion to the partition portion, fluctuates, or deviates from the predetermined relative rotational phase, a control for the relative rotational phase with reference to the most retarded angle or the most advanced angle cannot be performed appropriately, accordingly, there remains room for improvement.
A need thus exists for a variable valve timing control apparatus which is not susceptible to the drawback mentioned above.